ADC reference voltage of stm32f4-discovery

[sen2]

Posted on February 13, 2014 at 14:00

I use stm32f4-discovery board. I am working with the ADCs, and for my prpose I need to set the ADC reference VREF+ at 3.2V. in the reference manual RM0090 it is said that stm32f4 LQFP100 has VREF+ VDDA pin. But the discovery board doesn't have any of those. So how can I set the reference voltage to my requirement  in the Discovery board.

With regards,Souvik

[chen]

Posted on February 13, 2014 at 17:39

Hi

''in the reference manual RM0090 it is said that stm32f4 LQFP100 has VREF+ VDDA pin. But the discovery board doesn't have any of those. So how can I set the reference voltage to my requirement  in the Discovery board.'' You cannot on the Discovery board, unless you want to modify the Discovery board (cut tracks, add wires and components). '' I am working with the ADCs, and for my prpose I need to set the ADC reference VREF+ at 3.2V.'' I believe if you look at the schematic - the Vref is tied to the supply voltage. Which is 3V I think. What exactly are you trying to do/ measure? Bear in mind this guy blew up the CPU by putting a voltage higher than allowed : https://my.st.com/public/STe2ecommunities/mcu/Lists/STM32Discovery/Flat.aspx?RootFolder=%2fpublic%2fSTe2ecommunities%2fmcu%2fLists%2fSTM32Discovery%2fstm32f429&FolderCTID=0x01200200770978C69A1141439FE559EB459D75800084C20D8867EAD444A5987D47BE638E0F&TopicsView=https%3A%2F%2Fmy.st.com%2Fpublic%2FSTe2ec...

[Tesla DeLorean]

Posted on February 13, 2014 at 18:35

As I recall the regulator is 3V3 and there is a diode dropping you to 3V0, I suspect you could simply modify the circuit if you desired, and considered the consequences. The STM32F405 could definitely run at 3V3

[deanos]

Posted on February 13, 2014 at 22:18

Yes, just remove D3 (top right of PCB) and replace it with wire link to get 3.3V power rail which the STM32F4 will happily run at. You could also replace the regulator U1 with the 3.2V version (LP3985M-3.2) if you really need 3.2V.